1. Field of the Invention
This invention relates to a zeolite catalyst, such as a MFI, L or (3 zeolite on which platinum, germanium and aluminum have been deposited. One use of this zeolite catalyst is for conversion of aliphatic hydrocarbons, such as propane, to aromatic hydrocarbons, such as benzene, toluene and xylenes.
2. Description of the Prior Art
Zeolite is a crystalline hydrated aluminosilicate that may contain other metals in the framework of the zeolite crystal or deposited, exchanged or impregnated onto the zeolite. A method for preparing a zeolite comprises (a) preparing an aqueous mixture of silicon oxide and sources of oxides of aluminum; and (b) maintaining said aqueous mixture under crystallization conditions until crystals of zeolite form. Zeolite by itself is known as an operative catalyst for many hydrocarbon conversion reactions but selectivity to a particular product may be low. Much zeolite research has focused on modifying the zeolite by depositing particular elements or compounds on the surface of the zeolite.
U.S. Pat. No. 5,456,822 discloses an MFI zeolite in hydrogen form with silicon, aluminum and/or gallium in the framework; a matrix of a refractory oxide and at least one oxide of magnesium, aluminum, titanium, zirconium, thorium, silicon or boron; gallium; platinum and at least one other metal, such as tin, germanium, indium, copper, iron, molybdenum, gallium, thallium, gold, silver, ruthenium, chromium, tungsten and lead, as a catalyst for aromatization of hydrocarbons of two to nine carbon atoms per molecule.
U.S. Pat. No. 5,227,557 discloses an MFI zeolite with platinum and at least one metal of tin, germanium, lead and indium, optionally containing an amorphous matrix, as a catalyst for aromatization of hydrocarbons of two to four carbon atoms per molecule.